Filters for gases



Jan. 17, 1961 K. E. BUCKMAN FILTERS FOR GASES 5 Sheets-Sheet 1 Filed May 11, 1959 F/GZ.

F/GB.

In den tor Zzzw)? meaffizzc/imm B 5K4 A Home y 1961 v K. E. BUCKMAN 2,968,361 I FILTERS FOR GASES Filed May 11, 1959 5 Sheets$heet 2 f T I 7/@ L A; l LI. 6 8

Inventor firzzfzfi (5. 1920422422 By flMA Home y Jan. 17, 1961 Y K. E. B-UCKMAN 6 FILTERS FOR GASES Filed May 11, 1959 5 Sheets-Sheet :s

lnvenlor Fil ed May 11, 1959 K. E. BUCKMAN 2,968,361 FILTERS FOR GASES Jan. 17, 1961 5 Sheets$heet 4 Inventor ZZY/iaffi (ff 7K9; 5220592422.:

v By WM Attorney K. E. BUCKMAN FILTERS FOR GASES Jan. 17, 1961 5 Sheets-Sheet 5 Filed May 11, 1959 IW HIIIIH v I n ventor ZY/Z/Zi? 52/2!!! fizzzi w/v y fl gmzA Horne v v 2,968,361 FILTERS FOR GASES Kenneth Ernest Buckman, Redbridge, England, assign'or to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed May 11, 1959, Ser. No. 812,376 Claims priority, application Great Britain May 12, 1958 3 Claims. (Cl. 183-71) This invention relates to filters for fluids, and more particularly to air filters. Such filters are commonly fitted to the air intakes of internal combustion engines and may incorporate means for silencing the flow of air through the filter.

From one aspect, the invention is an air filter casing comprising an upper and a lower shell within which are a pair of opposed recessed portions or shoulders respectively adapted to engage opposite ends of a hollow filter element of pleated filter paper or like material so as to locate the element within the casing, said shells being adapted to be secured with opposite ends of the element clamped therebetween and said casing having one or more 'air inlet passages by which air entering the casing is brought into contact with the exterior of the element, one of the shells having an air outlet passage for the delivery of filtered air from the interior of the element.

The air inlet passages are preferably arranged so that air entering the casing is directed downwardly over the exterior of the element from the upper end thereof.

The recessed portions or shoulders may be respectively integral with the shells; alternatively one of the recessed portions or shoulders may beformed on a separate member carried by one of the shells and adapted to be resiliently pressed against one end of the filter elements when the two shells are secured together.

The two shells may be secured together by a nut and bolt connection or by means of a securing member which engages in aligned apertures at diametrically opposed points on the two shells.

The casing may have one or more openings in the lower part thereof to permit the ejection therefrom of dust or other solid particles which fall off the exterior of the filter element; such openings may be formed in one of the shells or may be between adjacent peripheral portions of the two shells.

From another aspect the invention comprises such a filter casing with such a pleated filter element therein to form an air filter.

Preferably the filter element comprises a strip of sheet filter material joined at its ends and folded about transverse fold lines to form a series of accordion pleats the ends of each of which are sealed'by means of adhesive applied to opposite longitudinal edge portions of the strip on one side thereof, adjacent pleats, and the two parts of each pleat, being spaced from each other by dimples or like spacer formations impressed in the strip; and the recessedportions or shoulders preferably each carry a gasket adapted to provide sealing contact with an end of the element adjacent the inner peripheral portion thereof.

The invention also extends to the construction and mounting of the pleated filter element.

The scope of the invention is defined by the appended claims; and the invention and how it can be performed is hereinafter particularly described with reference to the accompanying drawings in which:

Figure 1 is a plan of a portion of a strip of filter paper;

Figure 2 is a section on the line IIII of Figure 1;

Figure 3 is a diagrammatic end view illustrating how rates Patent C) 2,968,361 Patented Jan. 17, 1961 the strip of filter paper in Figure 1 is folded to form a filter element;

Figure 4 is a vertical section through a pleated filter element;

Figure 5 is an end view of part of the filter element shown in Figure 4;

Figure 6 is an elevation of one embodiment of an air filter for an internal combustion engine;

Figure 7 is an inverted plan of Figure 6;

Figure 8 is a vertical section on the line VIIIVIII of Figure 6;

Figure 9 is a section on the line IXIX of FigureS;

Figure 10 is a vertical section through a second embodiment of an air filter for an internal combustion engine; and

Figure 11 is a vertical section through a third embodiment of an air filter for an internal combustion engine.

In one preferred embodiment of the invention for use as an air cleaner and silencer for an internal combustion engine the filter element comprises a strip of filter paper 1 (Figures 1 and 2) impregnated with a thermosetting synthetic resin to give it a desired degree of porosity and stiffness.

Along each longitudinal edge of the strip 1 there is applied a strip of adhesive 2; and at regular intervals lengthwise of the paper strip there is impressed therein a series of parallel fold lines 3. The areas of the strip 1 betweenfold lines 3 to form a series of accordion pleats 10 the ends of which are sealed by bringing into apposition, and if necessary applying pressure to, the end portions of each part of a pleat 1i] coated with the adhesive 2.

The two ends of the strip are then joined so as to form the pleated strip 1 into a hollow filter element 11 in which the folds 12 at the outer periphery thereof are free but the folds 14 at the inner periphery are held contiguous to each other because of the sealed ends of the pleats 10. A strip 15 of paper is preferably secured by adhesive to the pleat folds 14 at the inner periphery of the element 11 at each end thereof, these strips 15 reinforcing the element 11, against peripheral tension thereon and improving the seal between the parts of the inner end portions of the pleats 10 at each end of the element 11.

The arrangement of the spacer dimples 4, 5, 6, 7 and 8 is such that, as shown in Figures 3 to 5, the free outer folds 12 of the pleats 10 are spaced from each other by sets of abutting dimples 4, 7 on the dirty air side of adjacent pleats of the filter element 11, and the two portions of each pleat 10 are spaced from each other on the clean air side of the pleats by dimples 6, 8 on one portion of each pleat in abutment with a plane surface on the other portion of each plea-t, and by dimples 5 on said other portion in abutment with a plane surface on said one portion. Preferably the pleats are formed with U-shaped folds at their inner and outer edges, this being conveniently effected by making the fold lines 3 of approximately W section. A tool for forming such fold lines 3 comprises a punch with a ridge of W section projecting therefrom and a die with a groove therein the section of which is that of a W with the central inverted V portion of the W truncated. The positions of the punch and die are reversed for alternate fold lines 3.

After the element 11 has been formed in this way it is preferably placed between a pair of formers and subjected to axial compression, the formers being shaped so as to form a chamfer of, say, 45 at the ends of the pleats 10 adjacent the inner periphery of the element 11, the annular chamfered surface 16 thus formed being adjacent a much less acutely sloping end surface 17 which extends about half way towards the outer periphery of the element from the inner periphery thereof at each end of the element. Such a construction facilitates proper sealing of the element in a casing therefor, as hereinafter described.

The casing of the air filter, shown in Figures 6 to 9 comprises an upper shell 20 and a lower shell 21, the lower shell 21 having a coaxial recessed portion 22 to form a shoulder 23 to receive one end of the element 11. The recessed portion 22 may be of elliptical shape, as shown in Figure 9, or of circular or other shape, and on the shoulder 23 a soft flexible gasket 24 is secured thereto by adhesive.

The outer peripheral portion 25 of the lower shell 21 is downwardly stepped and has secured thereto a silencer chamber 26 which communicates with the interior of the element 11 by way of one or more openings 27 in the central recessed portion 22 of the lower shell 21 and has a lateral outlet opening 28 to which is secured a flanged connector pipe 29.

The upper shell 20 has a peripheral wall 30 which is of D shape in plan and of a greater depth than that of the element; and the angular corner portions of the D-shaped wall 30 have secured therewithin arcuate pieces or fillets 31 which extend from the plane of the upper end of the element 11 to the lower end of the upper shell 20 so that the upper shell 20 has an inner peripheral wall which fits closely to the outer periphery of the filter element 11 and, at its lower end, engages over the outer vertical wall 32 of the downwardly stepped peripheral portion 25 of the lower shell 21 to form a peripheral trough 33 below the lower end of the filter element 11.

The end wall of the upper shell 20 has therein an inwardly extending central depression 35 which forms a seat for oneend of a helical spring 36 the other end of which is secured to the centre of a recessed plate 37 having a peripheral shoulder or flange 38 to which is secured a further gasket 39 adapted to be pressed against and seal the upper end of the element 11 under the action of the spring 36 when the shells 20 and 21 are secured together. The lower end of the spring 36 is conveniently secured to the plate 37 by forming a central depressed portion 40 therein which is continuously or locally crimped back at 41 to form a peripheral groove or a number of recesses so that the end of the spring 36 can be secured to the plate 37 by being clipped into the groove or recesses.

The base of the trough 33 formed by the interfitting peripheral portions of the upper and lower shells 20 and 21 is preferably formed with one or more openings 42 to enable dust which falls from the outer surface of the filter element 11 to be discharged from the casing.

The openings 42 may be in the form of localised spaces between the adjacent portions of the shells 20 and 21, or may be holes or (as shown in Figures 7 and 8), slots, and the latter may be half lanced so as to have vanes or fins adjacent thereto which will assist in the formation of eddies of air so as to promote the discharge of dust through the openings. The openings 42 are preferably placed at the lowest point or points on the trough 33 of the lower shell 21, and the portions of the shell 21 adjacent the openings 42 preferably slope downwardly towards the slots 42 so as to assist the migration of dust towards the openings under the action of gravity and vibration. Thus, the base of the trough 33 may slope towards its inner periphery. The location and shape of the openings 42 is preferably such that air currents within and outside the casing will assist the extraction of the dust deposited in the trough 33.

When assembling the filter the filter element 11 isplaced with its lower end resting on the gasket 24 in the lower shell 21, and the plate 37 carrying the other gasket39 is placed on the upper end of the element 11, the flange 38 on the plate 37 being uppermost. The upper shell 20 is then placed over the lower shell 21,,

the upper end of the spring 36 on the plate 37 locating itself about said depressed portion 35 in the end wall of the upper shell 20 and the spring 36 pressing the plate 37 downwards so as to bring the gaskets 24 and 39 into sealing contact with the ends of the filter element 11. The upper and lower shells 20, 21 are provided each with a pair of diametrically opposed holes in their lower peripheral portions and the holes are brought into register and the inturned ends 44 of a resilient wire bail or stirrup 45 are sprung into the aligned pairs of holes so as to secure the two shells 20, 21 together. The middle portion of the bail- 45 is secured by being sprung into position over the lower end of the silencer chamber 26, the latter conveniently having a recess 46 or like formation therein to retain the bail 45 in such position.

In order to provide communication between the outlet of the air filter 28 and a balance hole adjacent the inlet opening of a carburetter to which the air filter is to be secured, the connector pipe 29 secured to the outlet 28 of the filter silencer chamber 26 is made substantially oval or of other non-circular shape in cross section and has at its outer end a flange 50 over which is crimped the flange 51 of a face plate 52 which has therein a circular opening 53 adapted to register with the inlet opening of the carburetter, and one or more additional openings 54, 55 adapted to register at least partially with the balance hole or holes on the carburetter. The face plate 52 preferably also has integral extensions 56 adapted to be welded to the lower shell 21 of the filter so as to impart rigidity to the structure.

When the filter is in operation on an internal combustion engine, air enters the casing by way of the passages 57 provided between the arcuate fillets 31 and the angular corner portions of the D-shaped upper shell 20, the air then passing into the space in the upper shell 20 above the upper end of the filter element 11, and then downwardly over the outer surface and between the pleats 10 of the element 11, through the filter element 11 to the interior thereof, and thence by way of the silencer chamber 26 the outlet openings 28 at the end of the connector pipe.

Dust which accumulates on the filter element 11 can fall freely downwards in the spaces between adjacent pleats and into the trough 33 in the lower shell 21, in which it will gravitate towards the discharge openings 42 therein, as the result of vibration of the casing, particularly when the engine is operating at low speed. Any residual dust can be periodically removed from the trough 33 and the element pleats 10 by brushing.

It is found that the fall-out of dust from the element, and the elficiency and life of the latter maybe improved by lightly coating the outer surface of the element with a non-drying oil, using, say 10 to 20 gm. for each 500 sq. cm. of element area for this purpose. A convenient grade of oil is an S.A.E. 2O mineral oil. The oil apparently serves to agglomerate fine particles of dust into larger particles which are then more readily detached from the element by vibration during its use and have less tendency to clog the pores of the filter element. Other non-drying liquids may also be used.

In a further embodiment of an air filter according to the invention, shown in Figure 10, the gasket 39 for engagement with the upper end of the filter element 11 is secured to a recessed portion or shoulderv 59 of a plate which is integral with the upper shell 60 of the filter. In this construction the upper and lower shells 60 and 21 are secured together by means of a bolt 62 secured to the base of the silencer chamber 26 and which extends through a central opening in the recessed portion of the upper shell 60, and a wing nut 63 which is tight- I ened up on the bolt 62 so as to bring the upper and lower gaskets 39 and 24 into sealing engagement with opposite ends of the filter element 11.

The construction of this embodiment is otherwise the same as; that shown in Figures 6 to 9 and similar references are used in both embodiments to denote similar parts.

In a further embodiment of an air filter according to the invention shown in Figure 11 and using the filter ele ment 11 described above, the filter casing comprises an upper shell 70 and a lower shell 71, the lower shell 71 having a recessed portion or shoulder 72 on which is secured a sealing gasket 73. The lower shell 71 has a central opening 74 therein which forms an outlet for filtered air.

The lower end of a filter element 11 is seated on the gasket 73 and the upper end of the filter element is engaged by a further gasket 75 secured on a recessed portion or shoulder 76 of a metal plate 77. The plate 77 is downwardly pressed when the casing is assembled, as hereinafter described soas to bring the gaskets 75 and 73 into sealing engagement with opposite ends of the filter element 11, by means of a helical spring 78, the lower end of which abuts a washer 79 and the upper end of which abuts a central depressed portion 80 of the upper shell 70. The depressed portion 80 of the upper shell 70 has a central opening through which extends a bolt 81 which also extends through the spring 78, the washer 79, plate 77, the hollow space within the element 11 and the outlet opening 74 in the lower shell 71. The lower end of the bolt 81 is threaded at 82 and is adapted to be engaged in a carburettor to which the air filter is to be secured. A wire bail 84 is engaged in registering holes formed at diametrically opposed points on the lower peripheral portions of the upper and lower shells 70 and 71, in a manner similar to that described in relation to the embodiment shown in Figures 6 to 9, so as to hold the casing in its assembled condition when the shell 70 is placed over the shell 71 with the fil er element 11 pressed into engagement with the gaskets 75 and 73 by the spring 78. The assembled filter is then secured to the carburettor by tightening up the bolt 81 so as to bring a flanged seat member 83 adjacent the outlet 74 into abutment with a seat surface on the carburettor. The central portion of the wire bail is conveniently secured in a recess (not shown) on the side wall of the shell 70. In this form of construction air is admitted to the filter casing by way of an air inlet pipe 85 secured in an opening in the side wall of the upper shell 70. In this form of construction also the trough 86 formed in the lower shell 71 to receive dust which falls ofi the filter element 11 is not provided with dust ejection openings.

In all the embodiments of an air filter described herein it will be noted that the filter element 11 is held in sealing contact with sealing gaskets at the inner peripheral portions only of the element at opposite ends thereof, each pleat of the filter element being sealed at opposite ends of the pleat for the full width thereof by the sealing of the two parts of each pleat with the strips 2 of adhesive. The element 11 is also flexible, as each pleat is free from an adjacent pleat, apart from the inner peripheral portion thereof and an element having a given inner peripheral length can be fitted in filter casings of ditferent internal shapes (so that the filter element assumes for example an elliptical or other shape instead of a circular shape), provided that the seat surfaces for the opposite ends of the filter have the same peripheral length as the inner periphery of the filter element.

The treatment of the filter element with a non-drying oil or other liquid, as previously referred to herein, is

conveniently effected by spraying the oil on to one side of the filter paper (the side which will be on the dirty air side of the element) before it is creased and folded to form the filter element.

The required characteristics of the oil or other liquid with which the element is treated are that it should not volatilise to any substantial degree during the manufacture of the filter element, or during the normal life of the element in use or when stored; also the oil or other liquid should not harden to form a substantially impervious layer on the element during such conditions.

i[ claim:

1. In an air filter comprising an upper shell, a lower shell secured to said upper shell and defining a chamber therebetween, an annular pleated filter element disposed in said chamber and spaced from the ends thereof, a depression formed in said lower shell and extending into said chamber and into said filter element, a shoulder formed on said lower shell and around said depression, a gasket on said shoulder and engaging the inner peripheral portion of said filter element, a plate having a depression formed therein disposed in said chamber, said last named depression extending into said filter element, said plate having a shoulder formed thereon and around said depression, a gasket disposed between said shoulder and the inner peripheral portion of the upper end of said filter element, spring means between said upper shell and said plate to sealingly engage said gaskets and said shoulders and said filter element when said upper and lower shells are joined, and means for securing said upper and lower shells together.

2. An air filter comprising a D-shaped upper shell, an annular lower shell receivable in said upper shell and defining a chamber therebetween, an annular pleated filter element disposed in said chamber, the pleats of said filter element being adhesively joined at their upper and lower edges and spaced by a plurality of spaced and abutting dimples impressed therein, an inwardly extending depression formed in said lower shell and received in said filter element, an annular shoulder formed in said lower shell and about said depression for supporting said filter element, a gasket disposed between the inner peripheral edge of said filter element and said shoulder, a plate having an inwardly extending depression formed therein engaging the opposite end of said filter element from said depression in said lower shell, said plate having an annular shoulder formed thereon and about said depression and overlying the inner peripheral edge of said filter element, a gasket disposed between said last named shoulder and said filter element, spring means disposed between said plate and said upper shell to bias said plate into engagement with said filter element, means for securing said upper shell to said lower shell with said filter element clamped therebetween, a curved plate secured to said lower shell and extending into said chamber adjacent the flat portion of said upper shell, said curved plate and the fiat wall of said upper shell defining air inlet means communicating with said chamber and the outer surfaces of the pleats of said filter element, and air outlet means formed in said lower shell for conveying filtered air from said air cleaner.

3. The air filter set forth in claim 2 in which said lower shell has an opening formed therein for the discharge of solid particles falling from said filter element.

References Cited in the file of this patent UNITED STATES PATENTS 2,189,704 Campbell Feb. 6, 1940 2,569,243 Kovacs Sept. 25, 1951 2,720,279 James Oct. 11, 1955 2,732,031 Rabbitt et al. Jan. 24, 1956 2,732,356 Paxton Jan. 24, 1956 FOREIGN PATENTS 1,027,175 France Feb. 11, 1953 1,111,568 France Nov. 2, 1955 754,496 Great Britain Aug. 8, 1956 

